1. Field of the Invention
This invention relates generally to a method and apparatus for locating program segments on a record medium and, more particularly, to a method and apparatus for recording and detecting address code signals separating program segments on a magnetic tape.
2. Description of the Prior Art
It is known to record on a magnetic tape a number of program selections, such as music or songs, with spaces or pauses in the sound therebetween. It has been proposed that address signals be included to distinguish each of the program segments, so that random access is possible to facilitate locating a desired program. If the address signals are recorded in the blank or silent portions between each of the program segments, then those address signals should not result in an audible signal when the tape player is in the playback mode. For this reason, it has been proposed to employ address signals having a specific frequency, for example, 20 Hz, which is out of the conventional audible frequency band, so as not to be reproduced as an audible sound. Additionally, such address signals must be provided so that the desired program segment can be located whether or not the player is in the fast forward or in the rewind mode.
One specific problem involved in this type of program segment identification in a tape player is the requirement for such tape players to employ playback equalization circuits. For example, if the address signals are recorded as continuous sine waves, for example, of 20 Hz, and during playback the output from the playback magnetic head is fed to a playback equalizer circuit, the output signal therefrom will be distorted because the time constant employed for equalization is limited in its effectiveness only to those frequencies in the audible frequency band. Therefore, when the low-frequency address signals are to be transformed to the actual address code indicating the location of the specific program segment, the distorted signals produced by the playback equalizer will be detected with an inherent error caused, for example, by harmonics of the low frequency address signals.
Another problem relating to identifying program segments recorded on a magnetic tape is the provision of suitable signals, such that the desired program segment can be accessed randomly from either direction, that is, that the desired program segment can be located whether or not the tape player is operating in the fast forward or in the rewind mode.